Printed memory technology using polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) as a ferroelectric material is well known. Many reports describe ferroelectric properties for different compositions of PVDF-TrFE co-polymers, more specifically the ratio between VDF (vinylidene fluoride) and TrFE (trifluoroethylene). But the importance of the molecular weight is often neglected.
Experimental data has shown that electrical properties in memory devices that include PVDF-TrFE are improved when the molecular weight of the PVDF-TrFE is increased. For instance, the memories may be switched using a lower electric field.
The draw-back with high molecular weight polymers is that they are more challenging to synthesize and process. A very high molecular weight polymer is, for example, less soluble than a lower molecular weight polymer of the same chemical structure, and a solution of the high molecular weight polymer has a higher viscosity than that of a lower molecular weight polymer of the same chemical structure in the same solvent, which could be a disadvantage during purification (e.g., filtration) and coating. Therefore, there is a commercial interest in a PVDF-TrFE co-polymer with a lower molecular weight that exhibits ferroelectric properties similar to a high molecular weight PVDF-TrFE co-polymer.
One example of post-polymerization end group exchange is the treatment of a carboxyl-terminated PVDF-TrFE co-polymer (e.g., U.S. Pat. Nos. 6,809,166 and 6,828,388, assigned to Solvay Solexis S.p.A.) using F2 and UV light. This reaction exchanges the carboxyl functionality to a fluorine atom. This reaction may not be suitable for polymers other than substantially perfluorinated polymers and copolymers due to the extremely high reactivity of the fluorine gas.
This “Discussion of the Background” section is provided for background information only. The statements in this “Discussion of the Background” are not an admission that the subject matter disclosed in this “Discussion of the Background” section constitutes prior art to the present disclosure, and no part of this “Discussion of the Background” section may be used as an admission that any part of this application, including this “Discussion of the Background” section, constitutes prior art to the present disclosure.